Help!!!!! Rhode Island Red has no tail feathers!

Hi! I have two RIRs, two Barred Rocks, and two Australorps. They are all a almost two months old, and diveloping nicely. They have all their feathers exept on a few spots, and their tail feathers are beautiful. My problem is, that one of my RIRs named Penny, doesn't have any tail feathers. All she has are five pooffy little feathers. They are all really nice to each other so I am not concerned that the others are pulling Penny's tail feathers out. Is it just slow growth, or is there something wrong?

Penny is finally getting some tail feathers! Not a lot but a few! She still mostly has those puffy feathers. Did yours grow her tail feathers? I'm going to do some more research and try to load a picture. Thanks for all the help guys!